This invention relates to an oxygen concentration sensor suitable for use in sensing the concentration of oxygen in exhaust emissions of an internal combustion engine of an automotive vehicle, for example.
Oxygen concentration sensors of the prior art disclosed in U.S. Pat. Nos. 4,057,477, 4,127,464 and 4,141,813 are all constructed for mounting in an exhaust pipe of an automotive vehicle and are often splashed with water when the vehicle travels in rainy weather or is washed. If the water seeps through the cover and reaches the interior of the solid electrolyte member when its temperature is high, the solid electrolyte member is suddenly cooled. This may crack or rupture the solid electrolyte member, making it impossible for the member to generate an electromotive force.